Conventional zinc phosphate solutions coat in two or more layers of platelets and needle-like crystals. The layer closest to the metal surface is comprised of various ferrous phosphates in the form of crystallized platelets, which provide a base for the formation of the needle-like components of the upper coating, hopeite. The size, quantity and orientation of these hopeite crystals are extremely important in providing dependable corrosion inhibition and paint bonding qualities. In a conventional zinc phosphate coating the crystals formed range in size from 20 to 50 microns or even larger (as illustrated in photomicrograph FIGS. 1 and 3). Such crystals tend to form in a random three dimensional configuration, including some vertical growth with results in relatively large interstices between the crystals. Such interstices, in combination with the vertical growth of the large crystals, have been shown to adversely affect the adhesion performance of some cationic electrocoats. Such paints are preferred in some applications because of their superiority in supporting the anti-corrosion capabilities of the zinc phosphate base.
______________________________________ THE PRIOR ART U.S. PAT. NO. PATENTEE DATE ______________________________________ 1,610,362 COSLETT 12/4/26 1,911,726 TANNER 5/30/33 2,121,574 ROMIG 6/21/38 2,132,883 ROMIG 10/11/38 2,487,137 HOOVER 11/8/49 2,310,239 JERNSTEDT 2/9/43 3,333,988 DOUTY 8/1/67 2,132,000 CURTIN 10/4/38 ______________________________________